In this scripture passage we see three kinds of people. Natural man, Spiritual man and Spiritual man not growing but remaining a child still feeding on milk not solid food.I have demonstrated this with three plastic water bottles. one with lid closed represents natural man, without salvation. Even though the rain of God's mercy, grace, love is falling all around nothing gets inside since the lid is on. The second, the lid is open, some water may get in but doesn't fill the bottle quickly as the opening is narrow. The third is a bottle that you take a knife and chop of the top part, making the mouth very wide. This gets filled quickly.